The leaves are shredded as they are sucked through the screen. Large leaves like eastern maple work best and they must be dry.

If they don't get shredded on their way through the screen, they don't get through the screen and therefore should get recut. Supposedly it works very well - I haven't tried it yet although I now have one. Maybe I'll find out this Fall.

I have used one for decades. The expanded metal acts as a filter. It stops larger pieces and allows smaller ones to pass. Larger pieces eventually are cut up and pass as well. Thge screen does no cutting itself. There is no suction involved. The blade acts as a fan and blows the debris through the screen. The device works well on dry leaves. It makes the volume of leaves probably 4 or 5 times smaller. It doesn't work on pine straw. Pine straw and wet leaves will stop it up and removal of the unit is required to unstop it. (Major pain) If you have dry leaves with no pine straw it is great. Instead of 20 bags of leaves you will have only 4.